[Paleopsych] NYTBR: 'Warped Passages': The Secret Universe

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'Warped Passages': The Secret Universe
http://www.nytimes.com/2005/10/23/books/review/23folger.html

WARPED PASSAGES
Unraveling the Mysteries of the Universe's Hidden Dimensions.
By Lisa Randall.
Illustrated. 500 pp. Ecco/HarperCollins Publishers. $27.95.

    By TIM FOLGER

    IN 1900, the British physicist Lord Kelvin assured a gathering of his
    colleagues, "There is nothing new to be discovered in physics now."
    What a difference a century makes. Physicists today are all too aware
    of the holes in their theories. Lordly smugness isn't an option, not
    when physicists readily concede that more than 95 percent of the mass
    of the universe apparently consists of an unknown substance that,
    lacking any better description, they simply call dark matter. And just
    a few years ago astronomers discovered that the expansion of the
    cosmos is accelerating, driven by who knows what. Most vexing of all,
    physicists know that the two masterpieces of their discipline, quantum
    mechanics and general relativity, are incompatible and cannot in
    themselves be the final word on the nature of reality.

    Lisa Randall's chronicle of physicists' latest efforts to make sense
    of a universe that gets stranger with every new discovery makes for
    mind-bending reading. In "Warped Passages," she gives an engaging and
    remarkably clear account of how the existence of dimensions beyond the
    familiar three (or four, if you include time) may resolve a host of
    cosmic quandaries. The discovery of extra dimensions - and Randall
    believes there's at least a fair chance that evidence for them might
    be found within the next few years - would utterly transform our view
    of the universe.

    Randall, a theoretical physicist at Harvard, writes from the trenches:
    she's been working on higher-dimensional models of the universe for
    several years now. Her work is a departure from mainstream physics, in
    particular from string theory, which has its own take on extra
    dimensions.

    According to string theory, the most fundamental constituents of
    matter and energy are not particles, but infinitesimally small strings
    and loops that vibrate in 10 dimensions. The extra dimensions, string
    theorists contend, are so small and tightly curled that they are
    beyond the reach of any conceivable particle accelerator. Many
    physicists are willing to overlook the lack of experimental evidence
    because they believe that string theory will eventually reconcile
    quantum mechanics, which governs atoms and all other particles, with
    general relativity, which describes how matter and gravity interact on
    the very largest scales.

    Randall, though, argues that without any experimental feedback, string
    theorists may never reach their goal. She prefers a different
    strategy, called model building. Rather than seeking to create an
    all-encompassing theory, she develops models - mini-theories that
    target specific testable problems and that might then point the way to
    a more general theory.

    The models that Randall and her collaborator Raman Sundrum have been
    building may explain one of the greatest mysteries in physics: why is
    gravity so weak compared with the other forces in the universe?
    Gravity's weakness may not seem obvious, but as Randall writes, "A
    tiny magnet can lift a paper clip, even though all the mass of the
    earth is pulling it in the opposite direction." The electromagnetic
    force is a trillion trillion trillion times as powerful as gravity.

    To account for gravity's feebleness, Randall and Sundrum borrow some
    ideas from string theory but add their own twist. What if, they ask,
    higher dimensions are not small and curled up but large, perhaps
    infinite in size? Would there be any observable consequences? So they
    build models of what the universe might look like if it consisted of
    objects called branes (short for "membranes"). Branes, a creation of
    string theory, are surfaces that exist in higher-dimensional space. In
    Randall and Sundrum's various models, our universe is a
    four-dimensional brane (three dimensions of space and one of time)
    that exists on the surface of a five-dimensional space, much as a
    two-dimensional layer of water covers a three-dimensional sea.

    Their models, it turns out, produce a weakened gravitational force.
    But most important, they predict the existence of particles that may
    be detectable when a giant new particle accelerator called the Large
    Hadron Collider, under construction near Geneva, begins smashing
    protons together in 2007. The expectation is that the collider will
    discover a group of new particles, and perhaps even miniature black
    holes. If Randall and Sundrum's predictions pan out, and the existence
    of extra dimensions is confirmed, it would be one of the biggest
    advances in physics in decades.

    To set the stage for all this, Randall has to recap nearly a century
    of physics, which she accomplishes with extraordinary clarity. Her
    explanation of the uncertainty principle, a central tenet of quantum
    mechanics, is the best I have ever read. Along the way she includes
    some surprising historical sidelights. Dalí's "Crucifixion," she
    points out, depicts a four-dimensional cube. The full lyrics of "As
    Time Goes By" include a reference to Einstein and the fourth
    dimension. Einstein's calculus teacher, Hermann Minkowski, called his
    most famous pupil a "lazy dog." And Randall's perspective as a woman
    in a field where men hold 90 percent of all faculty positions makes
    for some wry comments. I doubt it would occur to most physicists to
    observe, "If, however, you lived inside a black hole, your travel
    opportunities would be far more severely constrained, more restricted
    even than those of women in Saudi Arabia."

    Some of her devices are a bit silly - for example, she opens each
    chapter with the adventures of time-and-interbranal-traveling
    characters named Athena and Ike Rushmore. Perhaps it's an occupational
    hazard: physicists who write for the general public often seem not to
    trust their own material. But a little silliness in a book that's
    freighted with discussions of gauge bosons, supersymmetry and D-branes
    is not necessarily a bad thing. In any case, none of her words are
    sillier than Lord Kelvin's.

    Tim Folger is a contributing editor at Discover magazine and the
    series editor for "The Best American Science and Nature Writing," an
    annual anthology.